The present invention relates generally to data routing systems, and more particularly to methods and apparatus for efficiently routing packets through a network.
In packet switched communication systems, a router is a switching device that receives packets containing data or control information on one port, and based on destination information contained within the packet, routes the packet out another port to a destination (or an intermediary destination). Conventional routers perform this switching function by evaluating header information contained within a first data block in the packet. The header includes destination information that can be used in determining the proper output port for a particular packet.
Efficient switching of packets through the router is of paramount concern. Referring now to FIG. 1, a conventional router includes a plurality of input ports 2 each including an input buffer (memory) 4, a switching device 6 and a plurality of output ports 8. Data packets received at input port 2 are stored at least temporarily, in memory 4 while destination information associated with each packet is decoded to determine the appropriate switching through switching device 6.
Data packets include both header and data fields and can be of variable lengths. The header includes both format information related to the type of packet and layer data. Networking protocols are defined in terms of layers, with each layer responsible for different portions of the communications in the network. For example TCP/IP is a standard internet network protocol that includes an application layer, transport layer, IP layer (network layer or L3), link layer (L2) and physical layer (L1). A data packet can include a plurality headers, one for each relevant layer that is to handle the packet during routing. Each layer header can include source and destination information as well as other layer specific information. To transfer the packet out of the switch, portions of the header are required to be examined (e.g., Layer 2 and Layer 3, L2 and L3 respectively, header information). Typically, packets are stored in memory 4 while header processing is performed.
Complicating the examination process, the format of the packet headers can vary. Destination or other information (e.g., L3 information) may not always be located at the same position in a header.
Unfortunately, conventional routers are inefficient in a number of respects. Conventional routers are incapable of processing packets in-line. All of the packet header typically must be received prior to the beginning of header processing. Packets are not screened early on for faults necessitating additional bandwidth and resources for handling these bad packets.